Check Working Gas Inlet Pressure; Flue Gas Analysis; Checking The Flue Integrity - Worcester GR8700iW 35 C Installation And Maintenance Instructions Manual

Inspection and maintenance
FAN PRESSURE TEST
Clean the Heat Ex.
Appliances
GR8700iW 30:
- 3.5
GR8700iW 35:
GR8700iW 40:
GR8700iW 45:
GR8700iW 50:
0 -1 -2
Fig. 75 Fan pressure test values
If the manometer reading is higher then the appliance output value
[P] mbar.
▶ The heat exchanger/exhaust path/siphon does not require attention.
If the manometer reading is out of tolerance, between 0 mbar and the
appliance output value [P] mbar then carry out the following checks.
▶ Check that the siphon is not restricted or blocked.
▶ Check the exhaust paths for restrictions.
▶ Clean the heat exchanger with a suitable cleaning tool, refer to
cleaning section.
▶ Re-check the fan pressure readings.
If the boiler, after completing the above checks, fails the fan pressure
test then contact Worcester, Bosch Group for advice.
▶ Replace test point cover after completing pressure check.
8.6

Check working gas inlet pressure

NOTICE:
Gas inlet pressure
▶ Do not continue with the other checks if the correct gas inlet pressure
can not be achieved.
▶ Check the gas supply working pressures in the system conform to the
readings shown in the table shown in section 6.6 "Checking gas inlet
pressure".
8.7

Flue gas analysis

NOTICE:
Combustion testing
▶ Combustion testing must be carried out by a competent person.
Testing must not be attempted unless the person carrying out the
combustion check is equipped with a calibrated flue gas analyser
conforming to BS 7967 and is competent in its use.
Flue gas analysis
▶ Ensure that the gas inlet pressure has been checked and is
satisfactory.
▶ Refit the test point plugs after the test has been completed.
▶ Set the appliance to maximum and minimum output in chimney
sweep mode for the flue gas analysis checks ( chapter 6.4).
▶ Check that the readings conform to those given in the following
tables. In addition to CO and CO/CO
maximum and minimum CO
2
56
Heat Ex. ok
- 10.0
- 5.0
- 4.8
- 6.0
-3 -4 -5 -6 -7 -8 -9 -10
mbar
0010025180-001
ratio checks also check the
2
percentage reading.
Maximum rated output
Gas type CO O
2 2
Natural gas 9.5 % 4.0 % <250ppm 8.6 %
± 0.4
Liquid 10.8 % 4.6 % <250ppm 10.2 %
propane (LPG) ± 0.4
Table 22 CO and O contents
2 2
If the CO is out of tolerance then please check:
2
▶ The gas inlet pressure.
▶ The gas rate.
▶ The fan test pressure.
▶ The flue and air intake, plus any possible blockages in the condensate
disposal.
▶ The condition of burner.
▶ For leaks or obstructions in the exhaust paths.
▶ CO is correctly adjusted.
2
The gas valve and venturi are factory set and should not need to be
adjusted, if found to be out of tolerance and when all other possible
causes have been checked, please contact the Worcester Bosch Group
Helpline 0330 123 3366.
8.8

Checking the flue integrity

NOTICE:
▶ Check flue joints are secure, the terminal and the terminal guard, if
fitted are clear and undamaged.
▶ Combustion testing must be carried out by a competent person.
Testing must not be attempted unless the person carrying out the
combustion check is equipped with a calibrated Flue Gas Analyser
conforming to BS 7967 and is competent in its use.
Flue gas analysis
▶ Ensure that the gas inlet pressure has been checked and is
satisfactory.
▶ Refit the test point plugs after the test has been completed.
▶ Refer to section 6.10 "Checking flue integrity" and check that the
readings conform to those given, confirming flue system and
combustion circuit are ok.
Greenstar 8000 Style – 6720883864 (2019/02)
Minimum rated output
CO CO O CO
2 2
5.5 % <75ppm
± 0.4
5.5 % <75ppm
± 0.4